Productivity of off-highway and heavy vehicles is typically correlated to several factors, such as performance in a number of ways. Examples of these factors are drivability of the vehicle and reliability of the vehicle. Recently, vehicle manufacturers have expended great efforts to improve performances of such vehicles, pushed by stringent customer requirements and a high competitiveness of global markets. Modern engines and transmissions have recently integrated sensors and control algorithms that have significantly increased vehicle performance, allowing these vehicles to operate under critical conditions while still being able to traverse large distances. Driveline components of such vehicle may be complex subsystems that integrate auxiliary functions, which can enhance the usability and flexibility of off-highway vehicles. In particular, a vehicle may include an integrated central tire inflation system (CTIS) that provides for inflation or deflation of the tires of the vehicle through an on-board pump and a set of rotary joints integrated into wheel hubs. Wheel hubs used with a rotary joint of a CTIS are complex components from a mechanical point of view, but such increased complexity provides many advantages over conventional wheel hubs.
Wheel hubs are mechanical components in which movement and torque are transferred from drive shafts into the axle to the wheel. Off-highway vehicles are designed to work in tough conditions and therefore wheel hubs used with off-highway vehicle must also do the same. The components of the wheel hubs are enclosed to protect them from an external operating environment. In addition, the mechanical complexity of wheel hubs can increase even more when they include additional functionalities, such as the forming a portion of a CTIS.
CTIS are on-board vehicle systems that allow an operator of the vehicle to inflate and deflate tires to improve drivability and fuel consumption of the vehicle in response to a wide range of driving surfaces. FIGS. 1A, 1C, and 1E illustrate a state of a tire in three conditions the vehicle including a CTIS may traverse. FIGS. 1B, 1D, and 1F illustrate a “footprint” of the tire against a surface the vehicle including a CTIS may traverse. High tire pressures, shown in FIG. 1A, are used on hard surfaces, such as but not limited to tarmac, to reduce rolling friction, which decreases fuel consumption at higher speeds. Low tire pressures, shown in FIG. 1E, are used on loose surfaces where a large tire footprint reduces a contact pressure, which improves vehicle grip and drivability. Medium tire pressures, shown in FIG. 1C, are used in intermediary circumstances where good grip is required and where some amount of tire deflection is useful. The core component of the CTIS is the rotary joint, which allows high pressure air flowing through conduits forming a port of or placed adjacent the axle into the rotating tire. Rotary joints in general comprise a first ring-shaped component fixed to the axle or a steering arm, a second ring-shaped component fixed to a rim of the wheel, and a series of sealing gaskets, typically sealing lips, that retain high pressure air inside an interface volume between the two ring shaped components. FIGS. 2A and 2B schematically illustrate an exemplary embodiment of a wheel hub 200 including a rotary joint 202 known in the art. The rotary joint 202 shown in FIGS. 2A and 2B further includes a dirt excluder 204, which is a gasket used to protect the mechanical portions of the rotary joint 202 from undesired dust particles.
A wheel hub that allows for a monitoring of the sealing gaskets used within while also allowing a torque delivered to the wheel to be estimated is not known in the art. Encoders integrated into wheel hubs to measure the rotational speed of the wheel, however, are known in the art. For example, U.S. Pat. No. 6,538,426 to Enrietto et al., discloses a combined hub temperature and wheel speed sensor system.
It would be advantageous to develop a wheel hub for use with a central tire inflation system for a vehicle including integrated sensors and a method for processing information collected from such a wheel hub that increases a reliability of the wheel hub and provides information about torque delivered by the vehicle.